Electrical contact



June 12, 1962 J. R. AYMAR ELECTRICAL CONTACT Filed Feb. 17, 1959 ll, 3/a Q IN V EN TOR.

Q m A 5 m N 4 w v 3 f A M MW United States Patent 3,039,076 ELEQTRICAL CGNTACT Julian Robert Aymar, 2018 E. 67th St, Brooklyn 34, NY. Filed Feb. 17, 1359, Ser. No. 793,821 1 Claim. or. 339-252 This invention relates to an electrical contact of the banana plug variety, and apparatus and method for manufacturing the same.

There is a great need for easily manufactured banana plug electrical contacts which can be readily connected and disconnected from an electrical receptacle or mating part. Prior art does not fulfill the need because there are no easily manufactured electrical contacts of this type known in prior art. All previous attempts to fulfill the need have required numerous and varied machine processes to make and assemble the electrical contact, and even then the resulting contact was not always operationally eflicient.

One object of the present invention is the provision of a device providing a secure contact between the banana plug electrical contact and an electrical receptacle or mating part, yet allowing for the easy connecting and disconnecting of the electrical contact.

A second object is the provision of a banana plug electrical contact having a large contact area with the mating part.

Another object is the provision of a banana plug electrical contact, wherein the spring legs of the electrical contact are securely anchored in the electrical contact base.

Yet another object is an easy, simplified and inexpensive method of manufacturing the electrical contact spring legs.

A further object is a simplified and efficient method of securely assembling the spring legs with the base.

A still further object is the provision of an apparatus for efiiciently manufacturing the banana plug electrical contact.

Other objects of the present invention will become apparent in the course of the following specification.

In accomplishing the objects of the present invention it was found desirable to provide a banana plug electrical contact comprised of a base and resilient conductive spring legs which serve to form. the electrical contact with any suitable electrical mating part. The legs which form the banana shaped spring are securely anchored in the base by the action of a specially designed collet device which during assembly exerts uniform pressure on the base in a manner securely anchoring one end of the resilient legs in the base. The legs themselves are made from conductive laminar material, are easily formed into the banana shape, and by means of the collet device are easily, efliciently and inexpensively anchored in the base.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings, showing, by way of example, preferred embodiments of the inventive idea.

FIGURE 1 shows the spring legs prior to shaping, comprising, two strips of conductive material fastened together by ultra-sonic spot welding.

FIGURE 2 shows the spring legs prior to shaping fastened together by electric spot welding.

FIGURE 3 shows the spring legs prior to shaping fastened together by soldering.

FIGURE 4 shows the spring legs prior to shaping fastened together by a rivet.

FIGURE 5 shows a top view of the spring legs prior to shaping, fastened together by means of an extrusion on one strip extending through a hole in the other strip.

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FIGURE 6 is a section through the center of the strip of FIGURE 5 having the extrusion.

FIGURE 7 is a side View of the spring legs.

FIGURE 8 is an end view of the spring legs as seen from the base end of the legs.

FIGURE 9 is a perspective view of the base of the banana plug electrical contact with a section through the center of the base.

FIGURE 10 is a sectional View through the center of the banana plug electrical contact and the collet device, showing the collet device in position to fasten the spring legs in the base of the electrical contact.

FIGURE 11 is a sectional view through the center of the completely assembled banana plug electrical contact.

The banana plug electrical contact 10 is shown in FIG- URE 11 and comprises a spring member 11 and a base member 12. The base 12 or the opening 13, may be connected to an electrical connection (not shown). The spring 11 is connected to any suitable electrical mating part (not shown), and since the spring 11 and base 12 are both made of electrically conductivematerial an electrical connection results.

The spring 11 is made by taking two strips of resilient, electrically conductive material (such as a nickel-silver alloy), which are slightly curved both in the lateral and longitudinal directions (FIGS. 7 and 8) and fastening them together at right angles to one another.

Various methods may be used for joining the two strips. For example, FIGURE 1 shows two such strips 14 and 15 fastened together by an ultra-sonic weld 16.

FIGURE 2 shows two strips 17 and 18 fastened together by an electrical spot weld 19.

FIGURE 3 shows two strips 20 and 21 fastened together by solder 22.

FIGURE 4 shows two strips 23 and 24 fastened together by a rivet 25.

As is indicated in FIGURES 5 and 6, the two strips 26 and 27 may be fastened together by extending a hollow cylindrical extrusion 28 on strip 27 through a hole 29in strip 26 and then peening down the extruded upper portion 30.

Using the embodiment of FIGURES 5 and 6 as an example, after being fastened together strips 26 and 27 are bent by any known means into the form of the banana shaped spring 11 indicated in FIGURES 7 and 8. The spring legs 31, 32 and 33, 34 are formed from strips 26 and 27, respectively. FIGURE 7 shows in side view the spring 11, wherein the original longitudinal curvature of the strips 26, 2'7 may be seen, While FIGURE 8 is an end view of the spring 11, wherein may be seen the original lateral curvature of the strips 266 and 27. Both FIGURES 7 and 8 indicate that after being bent to shape the full end portions 31a, 32a, 33a, and 34a of spring 11 are adjacent to one another, thus forming a continuous curved equi-sided section.

Being shaped in this manner, and being made out of resilient material, the spring 11 possesses the necessary springiness for being easily connected and disconnected from mating electrical parts (not shown), for making electrical contact within the mating parts, and for securely fastening the legs 31, 32, 33, 34 in the base 1 2.

The base 12 shown in FIGURE 9 comprises a hollow cylindrical outer portion 35 having an upper surface 36, a post 37, an upper portion of the post 38, a ledge 39 located below the level of surface 36, and a circular recess groove 40 having a bottom 41 separating the post 37 and the outer portion 35. A wing portion 42, connects the post 37 and outer portion 35 with the connector portion 43 which connects to any suitable electrical connection (not shown).

To securely fasten the spring 11 to the base 12, the

spring legs 31, 32, 33, 34 are placed in the recess groove 40 until the end portions 31a, 32a, 33a, 34a, touch the bottom portion 41 of recess grooves 49. (FIGS. 7, 9, and 10.) The spring 11 is so designed that when placed in the recess groove 40 the leg end portions 31a, 32a, 33a, 34a touch one another and completely cover the bottom portion 41 of the recess groove 40 (FIGS. 8 and 10). The banana plug electrical contact 10 is then placed in fixture 44 and is ready for the fastening operation to be carried out.

The collet device 45, as shown in FIGURE 10, includes a cylindrical tool body 46 having an inner tapered surface 47, and a collet 48 having an outer tapered surface 49. The slope of surface 49 is less than the slope of surface 47 when the collet 48 is in the open position, but the slopes are identical when the collet 48 is in the closed position. A threaded stud 50 is supported near one end by the tool body 46 by means of a nut '51 and washer 52, and at the other end it is connected to collet 48 by means of the threaded collet hole 53. The stud 50 passes through a heavy spring 54 which is pre-compressed between the tool body 46 and the collet 48 to any desired degree by tightening the nut 1.

FIGURE shows the relative positions of the holding fixture 44, the banana plug electrical contact 10, and the collet device 45 as the fastening operation is begun. When the collet 48 is fully open the collet bore or inner surface 55 is tapered and has a diameter sufficiently great so that the collet 48- may be slipped over the outer portion 35. The entire collet device 45 is then lowered until the bottom surface 56 of the collet 48 contacts the upper surface 57 of the fixture 44. This is the position shown in FIGURE 10. eration a downward force is applied on the upper surface 58 of the tool body 46. Since the slope of the collet surface 49 in the open position is less than the slope of the tool body surface 47 the collet 48 is compressed in- Wardly forcing the collet inner surface 55 against the outer portion 35 of the base 12. During this operation the collet bore or inner surface 55 changes from a tapered bore to a cylindrical bore thus forcing the thickened metal upper portion of the outer portion 35 to flow inwardly, and to securely hold the spring 11 against the post 37 and ledge 39. The spring 54, stud 50, and nut 51 can be adjusted to determine the diameter of the collet opening 55 in the open position. The slopes of surfaces 47 and 49 are selected such that the slope of surface 49 will become equal to the slope of surface 47 when the outer portion 35 has forced the spring 11 against the post 37 the desired amount. When the slope of surface 49 becomes equal to the slope of surface 47 no further increment of inward force can be applied by tool body 46 on the collet 48, nor, consequently, can any further increment of force be applied by collet 48 on the outer portion 35 of base 12. When the downward force on the tool body 46 is released the collet 48 reopens and the electrical contact 10 can be removed.

The resulting banana plug electrical contact is shown in FIGURE 11, where it can be seen how the leg 31 is held securely between the outer portion 35 and the post 37, and especially how the leg 31 is held against the ledge 39.

Among the advantages of this invention are:

To complete the fastening op- The ease of connecting and disconnecting the electrical contact from a mating part, the large area of contact with the mating part, the large contact area between the spring legs and the base, the simplified method or" manufacture of the spring, and the novel method of securely fastening the spring legs to the base.

It is apparent that the described examples are capable of various variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

What is claimed is:

An electrical contact of the banana plug type, comprising in combination with a spring member consisting of two strips having central overlapping portions wherein said strips are firmly joined together at right angles to each other, said overlapping portions being curved and constituting the projecting tip of said spring member, said strips further having spring legs extending side by side and curved in the lateral and longitudinal directions; a base member comprising a cylindrical outer portion, a wing portion integral with said cylindrical outer portion and extending transversely thereto, a post integral with said wing portion and located within said cylindrical outer portion, said base member having formed therein an annular recess groove separating said post from said outer portion, the spring legs of said strips having end portions located in said groove and contacting each other and the bottom of the groove and being in tight engagement with the adjacent surfaces of said post and said cylindrical outer portion to provide frictional securement of said leg end portions, said cylindrical outer portion having an annular upper surface, said post having a narrow upper portion extending above said upper surface and an annular ledge surrounding said upper portion and located below said upper surface, said strips having intermediate portions engaged tightly by said cylindrical outer portion against said ledge to prevent withdrawal of the spring member, the diameter of said intermediate portions being smaller than the diameter of the end portions located in said annular groove, whereby said intermediate portions provide an abutment preventing the withdrawal of the spring member.

References Cited in the file of this patent UNITED STATES PATENTS 2,377,912 Way June 12, 1945 2,398,684 Woodward Apr. 16, 1946 2,508,770 Oshinsky May 23, 1950 2,548,773 Chirelstein Apr. 10, 1951 2,563,561 Stanley Aug. 7, 1951 2,563,713 Frei et a1. Aug. 7, 1951 2,593,081 Wilmot Apr. 15, 1952 2,610,390 Locke Sept. 16, 1952 2,671,205 Wermine Mar. 2, 1954 2,794,963 Hess et a1. June 4, 1957 2,821,011 Sanders et a1. Jan. 28, 1958 2,846,563 Cronin Aug. 5, 1958 FOREIGN PATENTS 458,969 Germany Apr. 26, 1928 460,448 Great Britain Jan. 27,1937 809,169 France Dec. 3, 1936 

